The second is that as every scholar has to be skeptical about the traditions and the meaning of the words and everything else which he shall interpret, Erasmus was a scholarly skeptic. Luther couldn’t stand this. For him absolute statements in matters of ultimate concern are needed.
Third, Luther was a radical, in political and every other respect; but Erasmus seemed to be to him a man of adaptation to the political situation – not for his own sake but in order to have peace on earth.
Fourthly, Erasmus has a strongly educational point of view. The development of the individual in educational terms is decisive for him. And all humanism, up to today, has this educational drive and passion.
Fifth, Erasmus’ criticism is rational criticism. It is lacking in revolutionary aggressiveness.
Now all this Luther sees in Erasmus. But the whole discussion finally focused around the doctrine of the freedom of the will. Erasmus was for human freedom; Luther against. But now please don’t write that down without writing down everything I have to add now!: Neither Erasmus nor Luther doubted about man’s psychological freedom. They didn’t think man is a stone or animal. And even Karl Barth says: I know well that man is not a turtle – But he doesn’t know it well! because he doesn’t see that this means that man has freedom, freedom of deliberation and decision, freedom of contradicting himself, and that in this freedom which is his rational structure his image of God is implied.
Erasmus as well as Luther knew that man is essentially free, that he is man only because he is free. But now on this basis they drew opposite consequences. For Erasmus this freedom is also valid if you try to come to God. You can help God. You can cooperate with God, for your salvation. For Luther this is absolutely impossible.